Iran's opposition candidate Mir Hossein Mousavi has denounced the outcome of Friday's presidential elections, which the electoral commission says has resulted in a landslide victory for incumbent President Mahmoud Ahmadinejad.

With nearly all votes counted, state news agency IRNA reports that President Ahmadinejad has won 63 percent of the vote and Mr Mousavi 34 percent. Mr Mousavi, a moderate former prime minister, accuses the government of rigging the result. Both Iranian and foreign observers have expressed disbelief at the president's massive victory. Mr Mousavi's supporters have taken to the streets, clashing with those backing the president. Eyewitnesses say police used force to disperse opposition protesters earlier this week. Turnout in the election was a record 80 percent.